The invention relates generally to the location and entry of a lateral hydrocarbon well from a main wellbore in a subterranean formation, and additionally to treatment and/or analysis of a lateral hydrocarbon well after such location and entry.
Multilateral hydrocarbon wells, i.e., hydrocarbon wells having one or more secondary wellbores connecting to a main wellbore, are common in the oil industry, and will continue to be drilled in substantial numbers in the future. Location, or location and entry of one or more of the secondary or lateral wellbores, whether in completion or treatment procedures for a new well, or for reconditioning or reworking of an older well, often poses a problem for the well service operator.
A common approach for location and entry into lateral wellbores, particularly in level 1 and level 2 well construction, is to run jointed pipe from a service rig just barely into the lateral wellbore using standard location and kickoff procedures. Coilable tubing (commonly referred to in the industry as xe2x80x9ccoiled tubingxe2x80x9d) carrying a service or work tool is then run through the jointed pipe and into the lateral wellbore. In the usual approach, however, the extra expense of a service rig adds significantly to the cost of entry operations. Again, in some cases, even if the cost of the service rig is accepted, procedures employed for location of a particular lateral wellbore often lack precision and can be time consuming. Accordingly, efforts have continued, and there has been a need, to find an alternative to service rig dependent and inefficient approaches, particularly for level 1 and level 2 multilateral well reworking operations. In particular, there has been a need to provide an effective location or location and entry method and a locator, entry and servicing tool that would reduce costs and allow use of relatively inexpensive coiled tubing procedures. The invention addresses these needs, and provides a method, system, and tool for location, entry or re-entry, and service operations, each of which is particularly adapted to xe2x80x9ccoiled tubingxe2x80x9d usage.
Accordingly, in one embodiment, the invention relates to a method for location, or location and entry, of a lateral wellbore from a main wellbore of a multilateral hydrocarbon well, the method being characterized by unique operation of a controllable or controllably bent sub. In this embodiment, the working tool employed, including the aforementioned sub, which possesses particular required positioning and/or deflection characteristics, is operated in the main wellbore in a manner such that location of the desired lateral wellbore is facilitated. For conducting wellbore treatment or servicing, the work tool will comprise well treatment and/or analysis components, optionally in the xe2x80x9cbentxe2x80x9d segment or arm of the sub. Advantageously, with well treatment and/or analysis components provided in or near the sub, the invention permits immediate treating operations in the located lateral wellbore, tripping out and removal of the sub being unnecessary.
In a further aspect, the invention relates to a novel system for location or location and entry of a lateral wellbore from a main wellbore of a hydrocarbon well, and which further includes means for working or reworking the well, the system comprising a work string and a unique wellbore working tool suspended on the work string. The novel working tool terminates in a segmented work-locator sub having a terminal segment which may be xe2x80x9cbentxe2x80x9d according to predetermined design requirements. In particular, the work-locator sub of the system is adapted to semi-rigidly or semi-flexibly position its terminal segment or semi-rigidly or semi-flexibly deflect its terminal segment at an acute angle with respect to the longitudinal axis of the string or other segment of the sub, the terminal segment further being of a length adapted for lateral wellbore incursion. The terms xe2x80x9csemi-rigidlyxe2x80x9d and xe2x80x9csemi-flexiblyxe2x80x9d, as utilized herein with respect to the positioning or deflection of the sub terminal segment, are understood to indicate a relative rigidity at which the directing or positioning components of the sub are designed to maintain the position of or deflection of the sub""s terminal segment. This degree of rigidity is unlike the rigidity or stiffness at which common controllable bent subs are held during drilling operations. Instead, the sub of the system is structurally adapted for, or comprises structural components for, positioning the terminal segment with sufficient rigidity for efficient wellbore entry, as hereinafter described, while providing the capacity for, when the terminal segment is deflected from the longitudinal axis of the string or other segment of the sub, limited yield of deflection to a predetermined force or constraint or to a reduction of the angle of deflection in response to encounter of such force or constraint, or to an increase or expansion of the angle of deflection in the absence or elimination of such force or constraint. Accordingly, when the terminal segment is xe2x80x9cstraightxe2x80x9d, i.e., at least a section thereof is in or generally in a line coincident with the longitudinal axis of the remainder of the sub or the string, the sub""s terminal segment positioning components will be designed to hold the terminal segment with sufficient rigidity or firmness that the terminal segment does not pendulate or xe2x80x9cdanglexe2x80x9d to any significant extent due to gravity from the rest of the sub, a firmness important, for example, in wellbore entry, advancement, or retrieval. In the deflected posture of the terminal segment, the positioning components of the sub will be designed not only to provide the terminal segment with a certain moment to deflect or position and maintain the segment in deflection, but will be adapted to yield somewhat to the wellbore wall""s constraint, to adjust to a limited increase of the angle of deflection upon removal of any constraining force on the terminal segment, or to the de-crease of or reduction of the angle upon encounter by the terminal segment with a constraining force exceeding a pre-determined level. Thus, for example, the sub components are adapted or structured, on one hand, to maintain its terminal segment securely against the main wellbore wall, even though constrained thereby to some extent from further deflection, while, on the other hand, if the terminal segment is further or fully deflected during open lateral wellbore entry, being adapted for constraint and reduction of the degree of deflection to some degree, if, for example, the work tool is raised and the terminal segment again encounters the constraining wall of the main wellbore. To accomplish this type of resilient positioning or deflection, appropriate means are provided in the sub, as hereinafter described. Again, as utilized herein, the phrase xe2x80x9cof a length adapted for lateral wellbore incursionxe2x80x9d indicates that, in sizing the terminal segment for use in a main wellbore of specified width, the length of the terminal segment is sized to that length effective to protrude or project a section of the terminal segment into a lateral wellbore if the deflection angle between the longitudinal axis of the string or remainder of the sub and the longitudinal axis of the terminal segment is increased from the deflection angle determined by the intersection of the longitudinal axis of the string or remainder of the sub and the terminal segment when confined by a main wellbore wall. Importantly, the terminal segment of the work-locator sub of the system, in its most preferred aspect, further comprises means for well treatment and/or analysis so that, once the lateral wellbore is located and entered, the lateral may be worked, treated and/or measurements taken without withdrawal of the sub. Finally, means for orienting the work-locator sub in the wellbore and means cooperating with the work-locator sub for signaling the location of a lateral wellbore are provided in the system.
In a further particular aspect, the invention comprises a work tool which is adapted for performance in the invention method and which includes a combination of elements including a novel segmented work-locator apparatus or sub. In this embodiment, the novel segmented work-locator apparatus comprises a proximate attaching sub segment, attachable to a work string or tool at one end thereof, and a distal nose segment, preferably having a wellbore treating section, coupled to the attaching sub segment at the other end thereof, the two segments being coupled in such manner that the nose segment may be semi-rigidly positioned so that its longitudinal axis coincides at least substantially with that of the attaching segment, or may be pivoted and semi-rigidly positioned at an acute angle with respect to the longitudinal axis of the attaching segment, the nose segment being of a length adapted for lateral wellbore incursion. The terminal section may optionally contain analysis or measurement components, although commonly these will be located in the main body of the tool. Indication that the axis of the terminal segment coincides at least substantially with the axis of the work-string or another sub segment merely indicates that, while perfect alignment is desirable and included, it is not required, and that, with consideration of the length of the terminal segment, deviation from coincidence does not occur to the extent that entry into a main wellbore is prevented. Accordingly, in each of the sub embodiments described herein, the sub may be lowered into the main wellbore xe2x80x9cbentxe2x80x9d to some degree if the main wellbore width is of such extent that the widest angular extension of the terminal segment does not bring the terminal segment into significant contact with the main wellbore.
In yet a further embodiment, a novel controllably bent sub for location, location and entry, and treatment and/or analysis of lateral wellbores is described, the sub being characterized by unique operational capabilities. The sub of the invention is adapted for maintaining semi-rigid or semi-flexible positioning of its terminal member or segment in the manner described, and in its preferred form, is provided with novel force relief means to prevent damage to its components by excess fluid pressure generated force or by accidental undue constraint of the xe2x80x9cbentxe2x80x9d arm or terminal member of the sub. The novel sub of the invention is further provided with means for alerting or signaling an operator when the terminal segment of the sub is xe2x80x9cbentxe2x80x9d more than a predetermined amount, i.e., the acute angle of the sub has increased or become greater. Other novel and unique aspects of the method, system, and apparatuses of the invention are set out more fully in the following detailed description.